/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlineChatInterface.h
Delegate used when a chat message is received from a chat room
typedef TMulticastDelegate_ThreeParams< void, const [FUniqueNetId](API\Runtime\CoreOnline\Online\FUniqueNetId) &, const [FChatRoomId](API\Plugins\OnlineSubsystem\Interfaces\FChatRoomId) &, const [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [FChatMessage](API\Plugins\OnlineSubsystem\Interfaces\FChatMessage) > & > FOnChatRoomMessageReceived